Soundman,

You may be too far away or your speakers too close together (whichever way you want to look at it). Try sitting 8 feet away and see what happens. Alternatively, move them 4 feet apart. Experiment with this but start off by making an equilateral triangle between you and the speakers. This won't help with the sibilance but it should help with the soundstage.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated